Leaf miner flies
This is how to combat leaf miner flies
Leaf miner larvae eat their way through the inside of the leaf, leaving white/grey tunnels that make them easy to spot.
Treatment
This pest is very common and is divided into two subfamilies, which means that many plants serve as hosts for the larvae. Damage is usually limited. Crush individual larvae (usually at the end of their galleries) with your fingers or remove infested leaves. For more severe infestations, spray with nettle infusion, pyrethrum-based products (larvae are inside the leaves, contact is limited) or water (effect is delayed by a few days).
By Beatriz Moisset - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=76144908
